In the prior art "flux-brazing" method, it is a common practice to braze articles of aluminum or its alloy one to another by applying a brazing agent together with a flux to the abutting portion of the articles which are to be heated, wherein the flux is usually suspended in an appropriate liquid. In order to facilitate the manufacture of aluminum products, an aluminum brazing sheet has been employed as one or both of the brazed articles. The aluminum brazing sheet comprises a core sheet having its either or both surfaces clad with a skin layer, and this layer is composed of a certain brazing agent. The flux suspension is applied also to the abutting portions even if such a brazing sheet is employed and heated in the "flux-brazing" method.
Thus, both the brazing agent and the flux must be applied separately or successively to the brazed portions, whether the aluminum brazing sheet is or is not used. This has rendered comparatively intricate the operation in the prior art method of manufacturing the aluminum products. It is another drawback that the applied amount of flux is likely to vary among batches or products. An insufficient amount of the flux will cause an imperfect brazing, while a superfluous amount brings about other problems such as the residual flux in the brazed portions and the drippings of flux within a brazing oven. The flux residue will impair the appearance and the surface processability of the products, while the flux drippings polluting the oven.
A proposal was made and has been employed to avoid those problems resulting from the separate or successive application of the flux and the brazing agent. According to this proposal, a paste or liquid which comprises a binder or vehicle such as an acrylic resin containing a flux powder and an Al--Si powder as the brazing agent will be coated on the brazed portions, whereby the operation is simplified to a significant degree.
The existence of the binder in the brazed portions will however impair the brazing quality.
The present invention was made to resolve the problems referred to above in the prior art methods for "flux-brazing" aluminum materials or aluminum alloy materials. Therefore, an object of the invention is to provide a brazing agent comprising an aluminum alloy which contains a flux (hereinafter referred to as "flux-containing aluminum alloy brazing agent"), and also to provide an aluminum brazing sheet made partially of the flux-containing aluminum alloy brazing agent. The brazing agent and the brazing sheet in the invention are designed such that the variation in the applied amount of flux is eliminated improving the brazeability, the appearance of the brazed articles as well as the surface process ability thereof, and such that the brazing process is remarkably simplified.
Another object of the invention is to provide methods of making the "flux-containing aluminum alloy brazing agent" and the aluminum brazing sheet mentioned just above.